In the drilling, completion and production of oil and gas wells, different types of tubulars are employed. Thus, generally in the drilling operation drill pipe is employed, in the completion operation casing is employed, and in the production operation tubing is employed.
There are times when in all of the above described operations it is desirable and/or necessary to connect a tool into the pipe string, e.g., the drill string. For example, it is known to attach a wear belt to a drill pipe as disclosed in U.S. Pat. No. 4,146,060 to protect casing from wear by the drill pipe or to protect the drill pipe from wear by the casing or in an open hole. Still further, in many cases it is desirable that the tubular string, e.g., the drill string, have one or more centralizers connected along the length of the string.
Regardless of the nature of the tubular string, e.g., drill string, casing string, or tubing string, there can be circumstances where it would be desirable to have one or more tools connected to the outside of the tubular member, i.e. on its O.D. and which, depending upon the tool, could be replaced in the field by workers with a minimum amount of effort.